Ocular surgery, particularly when involving vision correction, is highly patient specific, being dependent on specific features and dimensions that in certain cases may be significantly different from those of expected norms. As a result, surgeons must rely upon their individual experience and skills to adapt whatever surgical techniques they are practicing to the individual requirements as determined by each patient's unique ocular structural features and dimensions.
To date, this individualized surgical adaptation is often accomplished essentially through freehand and best guess techniques based upon a pre-surgery examination and evaluation of each individual's ocular region and specific ocular features. This pre-surgical examination may include preliminary measurements as well as the surgeon making reference markings directly on the patient's ocular tissues with a pen or other form of dye or ink marking. Then, after the patient has been prepared and placed in a supine or prone position for surgery, as opposed to the often vertical seated positioning of the patient during the pre-surgery examinations, the surgeon adapts the placement and configuration of the initial surgical incisions to the actual physical dimensions and circumstances found in the patient as the surgical procedure begins and progresses.
Further complicating matters, ocular tissues are not conducive to pre-surgery reference markings or measurements. This is particularly true because most ocular tissues have wet surfaces diminishing the quality of reference markings. Even further still, many ocular surgeries involve internal physical structures that cannot be accessed for direct measurement or marking prior to surgery, and therefore, the pre-surgical markings on external surfaces must be visually translated onto the internal structures actually being modified. This translation often leads to undesirable post-surgical outcomes.
Additionally, pre-surgical rinsing, sterilization, or drug administration to the ocular tissues prior to or during surgery may dissolve, alter or even remove reference markings. Similarly, subsequent wiping and contact with fluids, including the patient's body fluids, during the surgical procedure may remove or distort any reference markings from the ocular region of interest. As a result, surgical reference markings may lose any practical effectiveness beyond the initial stages of the surgical procedure and in and of themselves are not accurate as they present broad lines to indicate, in some procedures, micro-sized incisions.
As such, there is a continuing need for effective reference indicia properly aligned with one or more particular ocular axis, especially when proper alignment of pre-surgical data is pivotal to satisfactory patient outcome. For instance, accurate rotational alignment of pre-surgical data with the ocular surgery is highly advantageous when making one or more limbal relaxing incisions on an eye to correct for varying degrees of astigmatism.
Astigmatism correction is a highly sophisticated surgical procedure that relies on delicate incisions within or on the limbus or cornea of an eye commonly known as limbal relaxing incisions (LRI) or astigmatic keratotomy (AK) to correct for a non-spherical topography of the eye. In the past, this delicate procedure has been performed based on partially accurate or even inaccurate visual measurements coupled with calculated incision templates based on those inaccurate visual measurements of a patient's eye. Past procedures have commonly relied on visual measurements prior to surgery and the subsequent inaccurate translation of those measurements to the limbal relaxing incision procedures where the positioning of the measured axis of the eye may have rotated and shifted. As a result, it is not uncommon for the placement of limbal or corneal relaxing incisions to be improperly aligned with the natural vertical axis of the eye, thereby resulting in residual astigmatism requiring glasses, and can include such side effects as poor visual acuity and shadows under low ambient light conditions.
Accordingly, in spite of the ongoing development and the growing sophistication of contemporary ocular surgery, there is a continuing need for the provision of effective reference indicia including data for making at least one limbal or corneal relaxing incision which is rotationally accurate relative to a patient's natural vertical axis or other important axis of orientation.